This work investigates the effect of the particle size of the mesoporous TiO2 electrode (mp-TiO2) on the photovoltaic performance of ternary semiconductor Pb5Sb8S17 quantum dot-sensitized solar cells (QDSCs). Due to the large particle sizes of ternary QDs (similar to 15 nm), the structure of a traditional TiO2 electrode needsmodification for the proper operation of a ternary QDSC. Liquid-junction Pb5Sb8S17 QDSCs were fabricated from Pb5Sb8S17 QDs synthesized by the successive ionic layer adsorption reaction process. The mp-TiO2 electrodes were prepared using two TiO2 particle sizes of 20 and 30 nm. The performance of the cells with 30-nm mp-TiO2 electrodes is 60% higher than that of the cells with 20-nm TiO2 electrodes. The best 30-nm cell exhibited a short-circuit current density of 14.21 mA/cm(2), an open-circuit voltage of 0.49 V, a fill factor of 44.9% and a power conversion efficiency (PCE) of 3.14% under 1 sun. At the reduced light intensity of 0.1 sun, the PCE increased to 3.95%, which is a 58% increase than the best previous result of 2.5%. The result reveals a general rule: the TiO2 electrode of a ternary QDSC should be constructed using large TiO2 particles (30 nm). (C) 2016 The Electrochemical Society. All rights reserved.